This program is concerned with the relation between the development of hypertension and altered electrolyte exchange of vascular smooth muscle. The specific areas of investigation related to hypertensive mechanisms are: (a) altered ion transport, (b) effects of transmural pressure, (c) small artery changes, (d) bioregulation, (e) effects of antihypertensive therapy, (f) comparison of hypertensive models, and (g) ultrastructure of vascular smooth muscle. The areas to be investigated related to transport mechanisms in vascular and intestinal smooth muscle are: (a) Na-K transport kinetics, (b) action of bioregulants on ion fluxes, and (c) Cl transport kinetics. The methods include: (1) isotope influx and efflux techniques for in-vitro vascular strips using 42K, 24Na and 36Cl, (2) computer analysis of efflux kinetics, (3) analysis of extracellular space using 60CoEDTA, (4) ion analyses (Na, K, Ca, Mg, Cl) using flame photometry and atomic absorption spectroscopy, (5) blood pressure with both direct and indirect techniques (6) contractile tension, and (7) electron microscopy.